The Influence of Heat Treatment on the Microstructure and Property of Ti-50Ni Alloy Fabricated by Selective Laser Melting

During the recent years, decade literatures have been published on the additive manufacturing (AM) Ti-Ni shape memory alloy because of the benefit for producing the intricacy structure and the concept of 4D manufacturing. In this paper, a Ti-Ni full density samples with the relative density access 99% compared with the traditional wrought samples was produced by the selective laser melting (SLM) technique using Ti-50at.%Ni power with the particle size distribution of 15-53micron. The volumetric energy density to build the SLM sample is 40J/mm3. The post-treatment was used to promote the mechanical properties and shape memory effect of the SLM samples. After solution treatment, the disrupted compression stress decreases with the strain upgrading. And after the hot isostatic pressing (HIP), the fracture compression stress and strain were all upgrade compared with the original and solution treated samples for 3350MPa and 42%. The transformation temperature range became narrow after the post-treatment. In all the situation, the samples were composed of the B2 and B19' atomic crystal structure for the AM technique identified by the X-ray diffraction. The microstructure exhibited anisotropy, which was formed columnar crystal and equiaxed crystal along and vertical to the building direction, respectively. The post-treatment couldn¡¯t change the grain type, only can promote the grains growth.